Traditional artist paints are oil-based wherein the oil is generally linseed oil. Such paints have been in use for at least the past three centuries and continue to retain popularity. Oil-based paints are often used in conjunction with a medium which allows the artist to adjust the rheology of the paint and adjust the pigment/binder ratio.
It has long been recognised that whilst linseed oil-based artist paints have many desirable properties, in use they suffer from two defects.
The first defect is a tendency to yellow. This has been found to be controllable within acceptable limits by a careful formulation.
The second and most serious defect is that of an uncontrollable tendency to become brittle with age. It is understood that this embrittlement is caused by continued oxidative polymerisation of the linseed oil, a process which cannot be arrested at any desired stage of "cure". This defect is particularly acute in both large and thickly painted oil paintings.
In order to circumvent these defects, the prior art has provided acrylic artist paints. It is notable that acrylic paints have achieved considerable popularity and that these paints do not suffer from the two defects of linseed oil-based artist paints. However, acrylic paint does not possess the "feel" of traditional oil-based artist paints. For that reason these paints are not generally used by "serious" artists.
Other attempts at meeting the embrittlement defect have been based on discovering formulations that were used by the various "oil masters". None of these attempts, to the present inventor's knowledge, have proved satisfactory.
Two other problems encountered in the use of artists' oil paints are shrinkage and "creep". Ageing oil paint films shrink as they age, and at a time in their ageing cycle when they are already too brittle to accommodate such movement without cracking.
"Creep" results, for example, in very heavy impasto applications of paint which often shrink and move about while the underlayers are still wet, causing the surface to crinkle.